Blanket neutronics of Li/vanadium-alloy and Flibe/vanadium-alloy systems for FFHR

Neutronics calculations were carried out to characterize self-cooled Li and Flibe blankets with vanadium alloy (V–4Cr–4Ti) structure, as advanced options for the Force Free Helical Reactor (FFHR-2). In the present paper, the parameter dependence of Tritium Breeding Ratio (TBR) and neutron shield performance was examined for a Li blanket (FFHR-LV) and a Flibe blanket (FFHR-FV). The TBR was independent from the Flibe composition between 30 and 45 mol% of BeF2 in the case of the FFHR-FV. Due to the increase in the temperature range of the coolant Flibe as a result of the change of the structural materials from JLF-1 (low activation ferritic steel) to V–4Cr–4Ti, the fraction of BeF2 can be changed from 43 to 31 mol% without changing the margin to coagulation of Flibe. The compositional change of Flibe resulted in a significant decrease in its viscosity. The decrease of TBR by the effects of MHD insulator coating with Er was negligibly small with the expected doping level of Er in the FFHR-LV. The increase in the B4C in the shielding material resulted in the decrease in the fast neutron flux at the superconducting magnet by 60–70% in both FFHR-LV and FFHR-FV. Optimum neutronics performance for the two blanket systems was derived by the calculation.